Microwave processing of thermoelectric materials and use of glass inclusions for improving the mechanical and thermoelectric properties

Abstract

According to an embodiment, there is provided a method of creating amorphous and amorphous-crystalline materials using microwave energy in the form of standing waves. The relatively quick processing time of the method allows investigating and creating a large number of material structures with various dimensions. An embodiment utilizes a scalable technique to produce high efficiency bulk thermoelectric structures as well as thin and thick.

1 . A method of producing an amorphous or amorphous-crystalline material, comprising the steps of:
 a. obtaining a quantity of a thermoelectric material;   b. configuring a microwave cavity to produce a standing wave when radiated by microwave radiation;   c. activating a microwave generator to produce said microwave radiation and said standing wave;   d. exposing the thermoelectric material to said standing wave for a length of time at least long enough to produce said amorphous or amorphous-crystalline material.   
     
     
         2 . A method according to  claim 1 , wherein said microwave generator operates at a frequency between 300 MHz and 300 Ghz. 
     
     
         3 . A method according to  claim 1 , wherein said thermoelectric material further comprises an amount of glass therein. 
     
     
         4 . A method according to  claim 1 , wherein said thermoelectric material is selected from the group consisting of Bi 2-2x Sb 2x , Te 3  (x=0.66 to 0.84), Bi 2 Se 3x Te 3-3x  (x=0.66 to 0.84), magnesium silicide (Mg 2 Si), higher manganese silicide (MnSi 1+n , n=0.73 to 0.75), silicon, silicon germanium (Si 1-x Ge x , x=0 to 1), iron silicide (FeSi 2 ), copper silicide, half-Heusler alloys, Skutterudites, clathrates, zintl phases, PbTe, zinc antimonide, oxide thermoelectrics, and organic thermoelectrics. 
     
     
         5 . A method according to  claim 3 , wherein said amount of glass is selected from the group consisting of a Si glass, a Ge glass, and a B glass. 
     
     
         6 . A method according to  claim 1 , wherein said thermoelectric material is rotated for at least a portion of the length of time it is exposed to said standing microwave signal. 
     
     
         7 . A method according to  claim 1 , wherein said standing wave signal has a voltage standing wave ratio between 1.0 and 2.0. 
     
     
         8 . A method according to  claim 1 , wherein said length of time at least long enough to produce said amorphous or amorphous-crystalline material is between a few seconds and a few hours. 
     
     
         9 . A method according to  claim 1 , wherein said thermoelectric material is in a powder form, a bulk form or a thin film form. 
     
     
         10 . A device for creating an amorphous or amorphous-crystalline material from a thermoelectric material, comprising:
 a. a microwave generator operable to produce a microwave signal;   b. a reflective partition, said reflective partition configured to reflect at least a portion of said microwave signal back toward said microwave generator;   c. a microwave cavity situated between said microwave generator and said reflective partition;   d. a sample container within said microwave cavity, said sample container configurable to house said thermoelectric material;   e. an isolator situated between said microwave cavity and said microwave generator; and,   f. a tuner situated between said isolator and said generator, said tuner adaptable to match a load created by said sample container to said microwave signal, said tuner and said partition operable together to creating a standing wave signal within said microwave cavity when said microwave generator is operating.   
     
     
         11 . A device according to  claim 10 , wherein said sample container comprises
 1. a microwave transparent housing, and,   2. a nonmetallic die within said microwave transparent housing, said die containing said thermoelectric material.   
     
     
         12 . A device according to  claim 11 , wherein said nonmetallic die is made of a material selected from the group consisting of boron nitride, magnesium oxide, alumina, zirconia, silicon carbide, sapphire, aluminum nitride, titanium diboride, quartz, and mullite. 
     
     
         13 . A device according to  claim 11 , wherein said microwave transparent housing is made of quartz. 
     
     
         14 . A device according to  claim 10 , wherein said reflective partition is movable. 
     
     
         15 . A device according to  claim 10 , wherein said reflective partition is a plunger. 
     
     
         16 . A device according to  claim 10 , wherein said tuner is a three-stub tuner or an E-H tuner. 
     
     
         17 . A method of producing a heterogeneous phase material, comprising the steps of:
 a. obtaining a quantity of a thermoelectric material;   b. configuring a microwave cavity to produce a standing wave when radiated by microwave radiation;   c. activating a microwave generator to produce said microwave radiation and said standing wave;   d. exposing the thermoelectric material to said standing wave for a length of time at least long enough to produce said heterogeneous phase material.   
     
     
         18 . A method according to  claim 17 , further comprising the step of:
 e. exposing the thermoelectric material to said standing wave for an additional length of time at least long enough to produce an amorphous or amorphous-crystalize material.   
     
     
         19 . A method according to  claim 17 , wherein said thermoelectric material is Si 0.8 Ge 0.2  and said heterogeneous phase material is Si 1-x Ge x  with x varying between 0 and 1. 
     
     
         20 . A method according to  claim 17 , wherein said thermoelectric material is Bi 0.5 Sb 1.5 Te 3  and said heterogeneous phase material is (Bi 2 Te 3 ) y (Sb 2 Te 3 ) z (Bi 2-2x Sb 2x Te 3 ) 1-y-z  with x, y, z each varying between 0 and 1. 
     
     
         21 . A method according to  claim 18 , wherein said thermoelectric material is a solid solution alloy A 1-x0 B x0  with a fixed x 0  and said heterogeneous phase material comprises A 1-x B x  with x varying between 0 and 1, wherein A and B are compounds or elemental materials.